AS al-Qaeda's spiritual and natural home, Yemen - the poorest country in the Middle East - is the new front line in the war against terror.

Its poverty, disaffected youth, political turmoil, terrain and impenetrable tribal system makes it the biggest ever challenge to the West's intelligence and special forces.

Corruption-riddled and politically volatile, it is almost perfect as a breeding ground for al-Qaeda, not least because it is where Osama bin Laden's father originally came from.

Analysts within MI6 identified Yemen as the new al-Qaeda front line as the 2003 Iraq invasion descended into all-out war by 2004.

By 2007, as Afghanistan also spiralled into all-out war and many jihadists fled, hundreds regrouped in Yemen and formed al-Qaeda in the Arabian Peninsular.

Britain's special forces teams and intelligence agencies have been training security police and developing a spy network in Yemen for the last three years.

The covert operation, based in and around the capital Sanaa, was launched as al-Qaeda loyalists fled Iraq and Afghanistan.

Now up to 1,000 al-Qaeda operatives are believed to be based there and are engaged in training recruits in Yemen.

The SAS's counter revolutionary warfare wing has been training Yemeni police and soldiers on how to combat al-Qaeda since 2007.

MI6 officers have, in conjunction with the domestic intelligence agency MI5, also developed a huge network of agents working undercover in Yemen. These agents, who have local knowledge and speak in convincing local dialect, are recruited from all over the Middle East and Britain.

They are paid for their work and neither MI6 and MI5 will ever confirm they have worked on Britain's behalf because this would endanger the agent's life.

It is believed that in the case of the the plane bombs discovered on Friday, the tip came from an MI6 officer responsible for Yemen who had been told by Saudi intelligence.

Of course we may never know the truth about how MI6 came to learn of the presence of a plane bombing attempt.

But there is no doubt that it came from a Middle Eastern source and since sources say many other plots have been disrupted in the past 18 months, it may already have saved many innocent lives.

Despite the effort being made there by our own agencies alongside US special forces and CIA agents, Yemen is still perfect for al-Qaeda.

Put simply, the republic has been too busy wrestling with its own security problems to engage fully with the al-Qaeda threat.

Despite having a relatively high percentage of its population in the military, it is a volatile nation.

On the one hand it has al-Qaeda trying to wrest control of the nation's religious and fanatical loyalty, on the other it is facing revolution to the north from Shia rebels.

The tribal system means that outside Sanaa much of the country is run by tribal chiefs, all known to one another. Yemen is a country pitted with contradictions. It has been a republic since the 60s and is the fastest-growing democracy in the Middle East - yet it suffers terrible corruption.

The Islamic faith is strong but the nation's motto is contradictory, depending on how you look at it: "Allah, al-Watan, ath-Thawra, al-Wehda" - "God, Country, Revoludomestic tion, Unity". Kidnapping is rife although traditionally indigenous hostages are treated with great respect until money is handed over in exchange for them.

Western hostages, however, have been killed - as have those found collaborating with western security forces or the local police.

The Yemeni economy is based on oil, the source of most of the government revenue.

But unlike the rest of the Arabian peninsula, its oil is predicted to run out in the next 10 years which could take the country to economic collapse.

Without economic aid Sanaa would actually run out of water.

Al-Qaeda thrives on instability in a country because it means lots of needy recruits looking for a cause, poor security and a government distracted by its own problems.